The present invention relates to an air filtration system for a vehicle cab, for such as a utility vehicle cab, such as for an agricultural tractor or harvesting machine.
Vehicle cab air filtration systems include an air recirculation circuit with an air recirculation blower arranged in an air recirculation channel system. The air recirculation blower draws air from the interior of the cab and blows this air back into the interior of the cab. An air recirculation filter is arranged in the air recirculation flow in order to filter contamination from the recirculating air.
In addition to a fresh air supply, air filtration systems for vehicles are frequently provided with an air recirculation circuit which recirculates the cab air, cleans it, heats it and/or air conditions it. Particular in utility vehicles, the air recirculation circuit may be separate from the fresh air supply and includes separate air recirculation filters.
In agricultural vehicles the fresh air carries a considerable load of contaminants such as dust and harvest residues, so that the fresh air filters are exposed to considerable contamination and must be cleaned or replaced frequently. It has therefore been proposed (EP-A-0 438 076) that the fresh air filters be arranged in such a way that they are accessible from the outside of the cab and so that any contamination of the interior of the cab during filter change can be avoided. It is also known to have fresh air filters which are accessible from the outside in the roof region of the vehicle. For example U.S. Pat. No. 4,648,311 describes a fresh air filter that is arranged in the side projection of the vehicle roof on a support element that can be pivoted downward about an axis for a filter change.
On the other hand, the air recirculation filters are generally not exposed to a high degree of contamination, but mainly filter out of the recirculated air the exhaust gases that have penetrated into the cab as well as cigarette smoke from an operator. Therefore, the service and replacement intervals for air recirculation filters are relatively long. Air recirculation filters are arranged inside the cab in corresponding flow channels and are accessible from the interior of the cab after removing sheathing components, covers and the like, and can be serviced and replaced such as described in U.S. Pat. No. 4,344,356. Due to the low degree of contamination no significant contamination of the interior of the cab occurs during service and filter change.
It has been shown, however, that in spite of the low degree of dirt, an air recirculation filter change within the cab can be problematical. In particular, if the vehicle is used in a toxic environment, such as during spraying with toxic spray material, toxic particles can penetrate into the cab. For example, the operator may carry such particles on clothing or shoes. Such toxic particles are filtered out of the recirculated cab air by the air recirculation filter and collect on the air recirculating filter. During filter change these particles can then penetrate into the interior of the cab.
Accordingly, an object of this invention is to provide an air filtration system which avoids contamination of the interior of the cab during a filter change.
An air filtration system includes an air recirculation circuit, which includes a air recirculation blower arranged in an air recirculation channel system. The blower draws air from the interior of the cab and blows it back into the interior of the cab. An air recirculation filter is arranged in the air flow conducted through the air recirculation channel. According to the present invention, the air recirculation filter is arranged in a portion of an outer wall of the cab roof behind a cover element. The cover hermetically closes the region of the air recirculation channel in which the air recirculation filter is located against the outside of the cab. The cover element can be removed or cleaned from the outside of the cab wall, so that the air recirculation filter is accessible from the outside.
With this air filtration system it is possible to access a contaminated air recirculation filter during filter service or a filter change from the outside. Contamination of the interior of the cab by toxic spray media (pesticides) and the like can be avoided reliably. A utility vehicle equipped with an air filtration system according to the invention thereby offers an absolute protection during spraying with toxic spray media. Furthermore, the air filtration system according to the invention offers very good accessibility to the air recirculation filter for the service and replacement of the filter.
Since the air recirculation circuit is closed air tight to the outside by the cover, no fresh air can penetrate into the cab over the air recirculation system.
Preferably, the cover closes an opening in a projection which projects to the side of the cab roof. The air recirculation filter is arranged behind the opening and is accessible from the outside when the cover is removed from the outer wall of the cab.
Preferably, the cover covers an opening on the underside of the sideways projection of the cab roof to assure good accessibility. For service operations or a filter change the cover can then be comfortably removed from below.
Preferably, the air recirculation filter is covered by a cover. The cover includes an opening through which one side of the air recirculation filter is connected with the air recirculation channel. This one side is, for example, the air inlet side of the air recirculation filter. Thereby, the covering forms a part of the air recirculation channel wall that conducts the recirculated air. Thereby, entry of fresh air from the outside is prevented.
Preferably, an air recirculation filter and a fresh air filter can be accommodated alongside each other in the roof of the cab, in particular in a projection of the roof of the cab. The section of the air recirculation channel in which the air recirculation filter is arranged is closed by a cover against the surroundings, while a fresh air channel in which the fresh air filter and the fresh air blower are arranged is connected with a fresh air inlet through which fresh air is drawn from the exterior of the cab. The fresh air inlet may be configured as a separate cover provided with inlet slots. This configuration simplifies the service operations and the filter changes which may be performed together if necessary for both filter types.
Preferably, the air recirculation filter and the fresh air filter are positioned next to each other in a fore and aft manner in a sideways projection of the cab roof.
Furthermore, the access to both types of filters is simplified by a single sheathing component which is attached to the outer contour of the cab and which covers the air recirculation filter insert and the fresh air filter insert.